Replacing animal-derived components in in vitro test guidelines OECD 455 and 487.

The evaluation of single substances or environmental samples for their genotoxic or estrogenic potential is highly relevant for human- and environment-related risk assessment. To examine the effects on a mechanism-specific level, standardized cell-based in vitro methods are widely applied. However, these methods include animal-derived components like fetal bovine serum (FBS) or rat-derived liver homogenate fractions (S9-mixes), which are a source of variability, reduced assay reproducibility and ethical concerns. In our study, we evaluated the adaptation of the cell-based in vitro OECD test guidelines TG 487 (assessment of genotoxicity) and TG 455 (detection of estrogenic activity) to an animal-component-free methodology. Firstly, the human cell lines A549 (for OECD TG 487), ERα-CALUX® and GeneBLAzer™ ERα-UAS-bla GripTite™ (for OECD TG 455) were investigated for growth in a chemically defined medium without the addition of FBS. Secondly, the biotechnological S9-mix ewoS9R was implemented in comparison to the induced rat liver S9 to simulate in vivo metabolism capacities in both OECD test guidelines. As a model compound, Benzo[a]pyrene was used due to its increased genotoxicity and endocrine activity after metabolization. The metabolization of Benzo[a]Pyrene by S9-mixes was examined via chemical analysis. All cell lines (A549, ERα-CALUX® and GeneBLAzer™ Erα-UAS-bla GripTite™) were successfully cultivated in chemically defined media without FBS. The micronucleus assay could not be conducted in chemically defined medium due to formation of cell clusters. The methods for endocrine activity assessment could be conducted in chemically defined media or reduced FBS content, but with decreased assay sensitivity. The biotechnological ewoS9R showed potential to replace rat liver S9 in the micronucleus in FBS-medium with A549 cells and in the ERα-CALUX® assay in FBS- and chemically defined medium. Our study showed promising steps towards an animal-component free toxicity testing. After further improvements, the new methodology could lead to more reproducible and reliable results for risk assessment.

Preferential Involvement of BRCA1/BARD1, Not Tip60/Fe65, in DNA Double-Strand Break Repair in Presenilin-1 P117L Alzheimer Models.

Recently, we showed that DNA double-strand breaks (DSBs) are increased by the Aß 42-amyloid peptide and decreased by all-trans retinoic acid (RA) in SH-SY5Y cells and C57BL/6J mice. The present work was aimed at investigating DSBs in cells and murine models of Alzheimer's disease carrying the preseniline-1 (PS1) P117L mutation. We observed that DSBs could hardly decrease following RA treatment in the mutated cells compared to the wild-type cells. The activation of the amyloidogenic pathway is proposed in the former case as Aß 42- and RA-dependent DSBs changes were reproduced by an α-secretase and a γ-secretase inhibitions, respectively. Unexpectedly, the PS1 P117L cells showed lower DSB levels than the controls. As the DSB repair proteins Tip60 and Fe65 were less expressed in the mutated cell nuclei, they do not appear to contribute to this difference. On the contrary, full-length BRCA1 and BARD1 proteins were significantly increased in the chromatin compartment of the mutated cells, suggesting that they decrease DSBs in the pathological situation. These Western blot data were corroborated by in situ proximity ligation assays: the numbers of BRCA1-BARD1, not of Fe65-Tip60 heterodimers, were increased only in the mutated cell nuclei. RA also enhanced the expression of BARD1 and of the 90 kDa BRCA1 isoform. The increased BRCA1 expression in the mutated cells can be related to the enhanced difficulty to inhibit this pathway by BRCA1 siRNA in these cells. Overall, our study suggests that at earlier stages of the disease, similarly to PS1 P117L cells, a compensatory mechanism exists that decreases DSB levels via an activation of the BRCA1/BARD1 pathway. This supports the importance of this pathway in neuroprotection against Alzheimer's disease.

Neuroprotection against Amyloid-ß-Induced DNA Double-Strand Breaks Is Mediated by Multiple Retinoic Acid-Dependent Pathways.

In this study, we have investigated the role of all-trans-retinoic acid (RA) as a neuroprotective agent against Aß 1-42-induced DNA double-strand breaks (DSBs) in neuronal SH-SY5Y and astrocytic DI TNC1 cell lines and in murine brain tissues, by single-cell gel electrophoresis. We showed that RA does not only repair Aß 1-42-induced DSBs, as already known, but also prevents their occurrence. This effect is independent of that of other antioxidants studied, such as vitamin C, and appears to be mediated, at least in part, by changes in expression, not of the RARα, but of the PPARß/δ and of antiamyloidogenic proteins, such as ADAM10, implying a decreased production of endogenous Aß. Whereas Aß 1-42 needs transcription and translation for DSB production, RA protects against Aß 1-42-induced DSBs at the posttranslational level through both the RARα/ß/γ and PPARß/δ receptors as demonstrated by using specific antagonists. Furthermore, it could be shown by a proximity ligation assay that the PPARß/δ-RXR interactions, not the RARα/ß/γ-RXR interactions, increased in the cells when a 10 min RA treatment was followed by a 20 min Aß 1-42 treatment. Thus, the PPARß/δ receptor, known for its antiapoptotic function, might for these short-time treatments play a role in neuroprotection via PPARß/δ-RXR heterodimerization and possibly expression of antiamyloidogenic genes. Overall, this study shows that RA can not only repair Aß 1-42-induced DSBs but also prevent them via the RARα/ß/γ and PPARß/δ receptors. It suggests that the RA-dependent pathways belong to an anti-DSB Adaptative Gene Expression (DSB-AGE) system that can be targeted by prevention strategies to preserve memory in Alzheimer's disease and aging.

Antagonizing functions of BARD1 and its alternatively spliced variant BARD1δ in telomere stability.

Previous reports have shown that expression of BARD1δ, a deletion-bearing isoform of BARD1, correlates with tumor aggressiveness and progression. We show that expression of BARD1δ induces cell cycle arrest in vitro and in vivo in non-malignant cells. We investigated the mechanism that leads to proliferation arrest and found that BARD1δ overexpression induced mitotic arrest with chromosome and telomere aberrations in cell cultures, in transgenic mice, and in cells from human breast and ovarian cancer patients with BARD1 mutations. BARD1δ binds more efficiently than BARD1 to telomere binding proteins and causes their depletion from telomeres, leading to telomere and chromosomal instability. While this induces cell cycle arrest, cancer cells lacking G2/M checkpoint controls might continue to proliferate despite the BARD1δ-induced chromosomal instability. These features of BARD1δ may make it a genome permutator and a driver of continuous uncontrolled proliferation of cancer cells.

Antifibrotic role of αB-crystallin inhibition in pleural and subpleural fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by myofibroblast proliferation and extracellular-matrix accumulation. IPF typically starts in subpleural lung regions, and recent studies suggest that pleural mesothelial cells play a role in the onset of the disease. The transition of mesothelial cells into myofibroblasts (mesothelio-mesenchymal transition) is induced by the profibrotic cytokine, transforming growth factor (TGF)-ß1, and is thought to play a role in the development and progression of IPF. The Mothers Against Decapentaplegic homolog (Smad)-dependent pathway is the main TGF-ß1 pathway involved in fibrosis. αB-crystallin is constitutively expressed in the lungs, and is inducible by stress, acts as a chaperon, and is known to play a role in cell cytoskeleton architecture. We recently showed that the lack of αB-crystallin hampered TGF-ß1 signaling by favoring Smad4 monoubiquitination and nuclear export. We demonstrate here, for the first time, that αB-crystallin is strongly overexpressed in the pleura of fibrotic lungs from patients with IPF and in rodent models of pleural/subpleural fibrosis. αB-crystallin-deficient mice are protected from pleural/subpleural fibrosis induced by the transient adenoviral-mediated overexpression of TGF-ß1 or the intrapleural injection of bleomycin combined with carbon particles. We show that αB-crystallin inhibition hampers Smad4 nuclear localization in pleural mesothelial cells and the consequent characteristics of mesothelio-mesenchymal transition. αB-crystallin-deficient mesothelial cells fail to acquire the properties of myofibroblasts, thus limiting their migration in vivo and the progression of fibrosis in the lung parenchyma. In conclusion, our work demonstrates that αB-crystallin may be a key target for the development of specific drugs in the treatment of IPF.

The small heat-shock protein αB-crystallin is essential for the nuclear localization of Smad4: impact on pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by the proliferation of myofibroblasts and the accumulation of extracellular matrix (ECM) in the lungs. TGF-ß1 is the major profibrotic cytokine involved in IPF and is responsible for myofibroblast proliferation and differentiation and ECM synthesis. αB-crystallin is constitutively expressed in the lungs and is inducible by stress, acts as a chaperone and is known to play a role in cell cytoskeleton architecture homeostasis. The role of αB-crystallin in fibrogenesis remains unknown. The principal signalling pathway involved in this process is the Smad-dependent pathway. We demonstrate here that αB-crystallin is strongly expressed in fibrotic lung tissue from IPF patients and in vivo rodent models of pulmonary fibrosis. We also show that αB-crystallin-deficient mice are protected from bleomycin-induced fibrosis. Similar protection from fibrosis was observed in αB-crystallin KO mice after transient adenoviral-mediated over-expression of IL-1ß or TGF-ß1. We show in vitro in primary epithelial cells and fibroblasts that αB-crystallin increases the nuclear localization of Smad4, thereby enhancing the TGF-ß1-Smad pathway and the consequent activation of TGF-ß1 downstream genes. αB-crystallin over-expression disrupts Smad4 mono-ubiquitination by interacting with its E3-ubiquitin ligase, TIF1γ, thus limiting its nuclear export. Conversely, in the absence of αB-crystallin, TIF1γ can freely interact with Smad4. Consequently, Smad4 mono-ubiquitination and nuclear export are favoured and thus TGF-ß1-Smad4 pro-fibrotic activity is inhibited. This study demonstrates that αB-crystallin may be a key target for the development of specific drugs in the treatment of IPF or other fibrotic diseases.

Discovery of novel potent ΔF508-CFTR correctors that target the nucleotide binding domain.

The deletion of Phe508 (ΔF508) in the first nucleotide binding domain (NBD1) of CFTR is the most common mutation associated with cystic fibrosis. The ΔF508-CFTR mutant is recognized as improperly folded and targeted for proteasomal degradation. Based on molecular dynamics simulation results, we hypothesized that interaction between ΔF508-NBD1 and housekeeping proteins prevents ΔF508-CFTR delivery to the plasma membrane. Based on this assumption we applied structure-based virtual screening to identify new low-molecular-weight compounds that should bind to ΔF508-NBD1 and act as protein-protein interaction inhibitors. Using different functional assays for CFTR activity, we demonstrated that in silico-selected compounds induced functional expression of ΔF508-CFTR in transfected HeLa cells, human bronchial CF cells in primary culture, and in the nasal epithelium of homozygous ΔF508-CFTR mice. The proposed compounds disrupt keratin8-ΔF508-CFTR interaction in ΔF508-CFTR HeLa cells. Structural analysis of ΔF508-NBD1 in the presence of these compounds suggests their binding to NBD1. We conclude that our strategy leads to the discovery of new compounds that are among the most potent correctors of ΔF508-CFTR trafficking defect known to date.

Long-term CFTR inhibition modulates 15d-prostaglandin J2 in human pulmonary cells.

Prostaglandins, the products of arachidonic acid release and oxidation by phospholipase A(2) and cyclooxygenases (COX) 1 and 2 respectively, are known as important inflammation mediators. However, their diversity in structure, properties and cell specificity make their physiological function difficult to define. In the lung, the prostaglandin D(2) (PGD(2)) metabolite 15d-PGJ(2) is known to modulate the properties of a large number of intracellular compounds, leading to both pro- and anti-inflammatory effects. In the lung, the serous sub-mucosal glands, that strongly express CFTR (cystic fibrosis transmembrane conductance regulator), play an important role in the defence against inflammation, and their derivatives Calu-3 cells are largely used in in vitro experiments. The present study was undertaken to determine whether the PGD synthase-PGD(2)-15d-PGJ(2) pathway is active in Calu-3 cells, and whether its activity requires a functional CFTR. Both cellular and released PGD(2) and 15d-PGJ(2) were measured in cells treated with CFTR inhibitors and stimulated or not with inflammatory IL-1ß. Pretreatment with either CFTR(inh172) or GlyH101 inhibitors decreased the basal cell content of both prostaglandins, and so did acute stimulation with IL-1ß, but the latter was dramatically reversed in CFTR(inh172)-treated cells. CFTR(inh172) also altered the release of inflammation mediators PGE(2) and IL-8, and this effect was blunted by exogenous 15d-PGJ(2). CFTR(inh172)-induced modulation of 15d-PGJ(2) cellular content was not detected in CFTR-silenced Calu-3 cells, but it was reproduced in pulmonary CFBE41o-cells, which express F508del-CFTR. These results show that cellular 15d-PGJ(2) production, which controls PGE(2) and IL-8 release, is disturbed by CFTR dysfunction. In Calu-3 cells, 15d-PGJ(2) production resulted from COX-2-regulated COX-1 activation, while CFTR(inh172)-induced alteration of 15d-PGJ(2) synthesis involved both decreased expression of PGD synthase and disturbed relationships between both COXs. CFTR-mediated regulation of PGD synthase-PGD(2)-15d-PGJ(2) pathway and cellular 15d-PGJ(2) effects may involve a large number of molecular reactive pathways. Their exploration should help understand the development of CF inflammation and might bring new perspectives in its treatment.

Disruption of cytokeratin-8 interaction with F508del-CFTR corrects its functional defect.

We have previously reported an increased expression of cytokeratins 8/18 (K8/K18) in cells expressing the F508del mutation of cystic fibrosis transmembrane conductance regulator (CFTR). This is associated with increased colocalization of CFTR and K18 in the vicinity of the endoplasmic reticulum, although this is reversed by treating cells with curcumin, resulting in the rescue of F508del-CFTR. In the present work, we hypothesized that (i) the K8/K18 network may interact physically with CFTR, and that (ii) this interaction may modify CFTR function. CFTR was immunoprecipitated from HeLa cells transfected with either wild-type (WT) CFTR or F508del-CFTR. Precipitates were subjected to 2D-gel electrophoresis and differential spots identified by mass spectrometry. K8 and K18 were found significantly increased in F508del-CFTR precipitates. Using surface plasmon resonance, we demonstrate that K8, but not K18, binds directly and preferentially to the F508del over the WT human NBD1 (nucleotide-binding domain-1). In vivo K8 interaction with F508del-CFTR was confirmed by proximity ligation assay in HeLa cells and in primary cultures of human respiratory epithelial cells. Ablation of K8 expression by siRNA in F508del-expressing HeLa cells led to the recovery of CFTR-dependent iodide efflux. Moreover, F508del-expressing mice topically treated with K8-siRNA showed restored nasal potential difference, equivalent to that of WT mice. These results show that disruption of F508del-CFTR and K8 interaction leads to the correction of the F508del-CFTR processing defect, suggesting a novel potential therapeutic target in CF.

Resveratrol rescues cAMP-dependent anionic transport in the cystic fibrosis pancreatic cell line CFPAC1.

BACKGROUND AND PURPOSE: The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-dependent chloride channel in the plasma membrane of epithelia whose mutation is the cause of the genetic disease cystic fibrosis (CF). The most frequent CFTR mutation is deletion of Phe(508) and this mutant protein (delF508CFTR) does not readily translocate to the plasma membrane and is rapidly degraded within the cell. We hypothesized that treating epithelial cells with resveratrol, a natural polyphenolic, phyto-ooestrogenic compound from grapes, could modulate both the expression and localization of CFTR. EXPERIMENTAL APPROACH: Cells endogenously expressing CFTR (MDCK1 and CAPAN1 cells) or delF508CFTR (CFPAC1 and airway epithelial cells, deriving from human bronchial biopsies) were treated with resveratrol for 2 or 18 h. The effect of this treatment on CFTR and delF508CFTR expression and localization was evaluated using RT-PCR, Western blot and immunocytochemistry. Halide efflux was measured with a fluorescent dye and with halide-sensitive electrodes. Production of interleukin-8 by these cells was assayed by ELISA. KEY RESULTS: Resveratrol treatment increased CFTR expression or maturation in immunoblotting experiments in MDCK1 cells or in CFPAC1 cells. Indirect immunofluorescence experiments showed a shift of delF508CFTR localization towards the (peri)-membrane area in CFPAC1 cells and in human airway epithelial cells. A cAMP-dependent increase in membrane permeability to halide was detected in resveratrol-treated CFPAC1 cells, and was inhibited by a selective inhibitor of CFTR. CONCLUSION AND IMPLICATIONS: These results show that resveratrol modulated CFTR expression and localization and could rescue cAMP-dependent chloride transport in delF508CFTR cells.

Cystic fibrosis transmembrane regulator inhibitors CFTR(inh)-172 and GlyH-101 target mitochondrial functions, independently of chloride channel inhibition.

Two highly potent and selective cystic fibrosis (CF) transmembrane regulator (CFTR) inhibitors have been identified by high-throughput screening: the thiazolidinone CFTR(inh)-172 [3-[(3-trifluoromethyl)phenyl]-5-[(4-carboxyphenyl)methylene]- 2-thioxo-4-thiazolidinone] and the glycine hydrazide GlyH-101 [N-(2-naphthalenyl)-((3,5-dibromo-2,4-dihydroxyphenyl)methylene)glycine hydrazide]. Inhibition of the CFTR chloride channel by these compounds has been suggested to be of pharmacological interest in the treatment of secretory diarrheas and polycystic kidney disease. In addition, functional inhibition of CFTR by CFTR(inh)-172 has been proposed to be sufficient to mimic the CF inflammatory profile. In the present study, we investigated the effects of the two compounds on reactive oxygen species (ROS) production and mitochondrial membrane potential in several cell lines: the CFTR-deficient human lung epithelial IB3-1 (expressing the heterozygous F508del/W1282X mutation), the isogenic CFTR-corrected C38, and HeLa and A549 as non-CFTR-expressing controls. Both inhibitors were able to induce a rapid increase in ROS levels and depolarize mitochondria in the four cell types, suggesting that these effects are independent of CFTR inhibition. In HeLa cells, these events were associated with a decrease in the rate of oxygen consumption, with GlyH-101 demonstrating a higher potency than CFTR(inh)-172. The impact of CFTR inhibitors on inflammatory parameters was also tested in HeLa cells. CFTR(inh)-172, but not GlyH-101, induced nuclear translocation of nuclear factor-kappaB (NF-kappaB). CFTR(inh)-172 slightly decreased interleukin-8 secretion, whereas GlyH-101 induced a slight increase. These results support the conclusion that CFTR inhibitors may exert nonspecific effects regarding ROS production, mitochondrial failure, and activation of the NF-kappaB signaling pathway, independently of CFTR inhibition.

A novel lipidomic strategy reveals plasma phospholipid signatures associated with respiratory disease severity in cystic fibrosis patients.

The aim of this study was to search for lipid signatures in blood plasma from cystic fibrosis (CF) patients using a novel MALDI-TOF-ClinProTools strategy, initially developed for protein analysis, and thin layer chromatography coupled to MALDI-TOF (TLC-MALDI). Samples from 33 CF patients and 18 healthy children were subjected to organic extraction and column chromatography separation of lipid classes. Extracts were analyzed by MALDI-TOF, ion signatures were compared by the ClinProTools software and by parallel statistical analyses. Relevant peaks were identified by LC-MSn. The ensemble of analyses provided 11 and 4 peaks differentially displayed in CF vs healthy and in mild vs severe patients respectively. Ten ions were significantly decreased in all patients, corresponding to 4 lysophosphatidylcholine (18:0, 18:2, 20:3, and 20:5) and 6 phosphatidylcholine (36:5, O-38:0, 38:4, 38:5, 38:6, and P-40:1) species. One sphingolipid, SM(d18:0), was significantly increased in all patients. Four PC forms (36:3, 36:5, 38:5, and 38:6) were consistently downregulated in severe vs mild patients. These observations were confirmed by TLC-MALDI. These results suggest that plasma phospholipid signatures may be able to discriminate mild and severe forms of CF, and show for the first time MALDI-TOF-ClinProTools as a suitable methodology for the search of lipid markers in CF.

Eicosanoid release is increased by membrane destabilization and CFTR inhibition in Calu-3 cells.

The antiinflammatory protein annexin-1 (ANXA1) and the adaptor S100A10 (p11), inhibit cytosolic phospholipase A2 (cPLA2alpha) by direct interaction. Since the latter is responsible for the cleavage of arachidonic acid at membrane phospholipids, all three proteins modulate eicosanoid production. We have previously shown the association of ANXA1 expression with that of CFTR, the multifactorial protein mutated in cystic fibrosis. This could in part account for the abnormal inflammatory status characteristic of this disease. We postulated that CFTR participates in the regulation of eicosanoid release by direct interaction with a complex containing ANXA1, p11 and cPLA2alpha. We first analyzed by plasmon surface resonance the in vitro binding of CFTR to the three proteins. A significant interaction between p11 and the NBD1 domain of CFTR was found. We observed in Calu-3 cells a rapid and partial redistribution of all four proteins in detergent resistant membranes (DRM) induced by TNF-alpha. This was concomitant with increased IL-8 synthesis and cPLA2alpha activation, ultimately resulting in eicosanoid (PGE2 and LTB4) overproduction. DRM destabilizing agent methyl-beta-cyclodextrin induced further cPLA2alpha activation and eicosanoid release, but inhibited IL-8 synthesis. We tested in parallel the effect of short exposure of cells to CFTR inhibitors Inh172 and Gly-101. Both inhibitors induced a rapid increase in eicosanoid production. Longer exposure to Inh172 did not increase further eicosanoid release, but inhibited TNF-alpha-induced relocalization to DRM. These results show that (i) CFTR may form a complex with cPLA2alpha and ANXA1 via interaction with p11, (ii) CFTR inhibition and DRM disruption induce eicosanoid synthesis, and (iii) suggest that the putative cPLA2/ANXA1/p11/CFTR complex may participate in the modulation of the TNF-alpha-induced production of eicosanoids, pointing to the importance of membrane composition and CFTR function in the regulation of inflammation mediator synthesis.